Evaporative Emission Control System (1989)
The system is designed to prevent harmful fuel vapor from escaping to atmosphere. The system consists of a vapor separator tank connected to fuel tank, and located between body inner and outer panels on right hand side of vehicle near rear wheel arch. An adsorption canister, containing activated charcoal, is positioned in engine compartment attached to front right hand fender valance. The two components are connected by a pipe running length of chassis. See Fig 2 .
A pressure relief valve is fitted in hose open to atmosphere, which would act as a safety valve should a build-up of pressure occur in system, for example if a hose became blocked or kinked. The volume of vapor emitted, in such an instance, would be acceptable. A pressure relief valve is also fitted in hose to adsorption canister and releases vapor to canister when pressure in separator reaches .75-1.0 psi.
In top of separator, a shut-off valve is incorporated in vapor exit port to prevent possible presence of any liquid fuel being transmitted to adsorption canister should vehicle roll over.
The adsorption canister, which is connected by hose to plenum chamber, absorbs and stores fuel vapor from fuel tank while engine is not running. The vapor is purged from canister by air drawn through an orifice in base of canister and by influence of vacuum at top. The vapor drawn into plenum chamber through a solenoid operated purge valve is finally burnt in combustion chambers. See Fig 3 .
The purge valve, which is attached to adsorption canister support bracket, is controlled by fuel injection E.C.U. which determines most emission acceptable time at which purging should take place. This will normally be at engine speeds above idle and when vehicle is in motion. A signal from E.C.U. to purge valve operates solenoid and opens valve to purge canister of fuel vapor.